For their new production of Sondheim’s Sweeney Todd, San Francisco Opera certainly hasn’t stinted on their stage blood budget. The intermission curtain shows a map of London with the Thames dyed blood-red, and there are enough squeam-inducing squirts of crimson onstage to make that almost plausible. In that and other respects, director Lee Blakeley’s staging is classic Victorian penny dreadful: dim lighting, plenty of hoop skirts, and melodramatic screams. It features a bare-bones two-story set with the usual darkly funny slide from the barber’s chair above to the pie shop below.

The inevitable question arises: What business does San Francisco Opera have putting on Sweeney Todd anyway? They sidestep the opera-versus-musical question by subtitling the show “The Demon Barber of Fleet Street: A Musical Thriller”. But this is definitely a musical, and staging it with opera singers in an opera house poses certain problems. Despite the use of light amplification for all the principals, the singers are not always audible. Their words are also very hard to understand. San Francisco Opera wisely chose to display supertitles, but it still would have been preferable to hear Sondheim’s witty lyrics rather than read them.

But this Sweeney Todd was also a chance to discover unsuspected theatrical talents in opera singers. Wagnerian mezzo Stephanie Blythe was the biggest revelation as the besotted baker, Mrs Lovett. Opera fans have long admired her crashing, vibrating waves of sound, but who knew she could also belt up a storm? Blythe has charisma, strong character acting skills, and impeccable timing. She even used her vibrato to great comedic effect during portions of “By the Sea”. Blythe could rock Broadway stages as well as she does opera houses.

Brian Mulligan hammed it up as Sweeney, with a brooding manner that bordered on the absurd. His rich baritone voice sounded appropriately foreboding, but didn’t consistently carry well over the (very loud) orchestra. As his friend (and Johanna’s lover) Anthony, Elliot Madore had similar issues. When he could be heard well, he had a sweet, expressive baritone voice. He also excelled in natural delivery of the dialogue. If only he’d had a more dramatically interesting role to play! His beloved Johanna was sung by Heidi Stober with unusual strength, a pleasant change from the chirpy sopranos who usually take the part.

Matthew Grills as Tobias surprised; the role is small and unmemorable throughout most of the show, but Grills’ pure and winsome tone during “Not While I’m around” astonished. His quiet, haunting portrayal of insanity at the end was also touching. The other character roles were well-filled: David Curry put on a delightfully over-the-top pseudo-Italian persona to play the barber Pirelli and caused many laughs when he suddenly revealed his Irish origins and accent. As the beggar woman, Elizabeth Futral foreshadowed her true identity well in her lucid moments without giving too much away or seeming too sane. Wayne Tigges and AJ Glueckert, as the Judge and Beadle, were the pictures of hypocrisy and corruption. Tigges’ deep bass-baritone was especially gripping during “Johanna”, a number with lechery and literal self-flagellation.

Perhaps the performers most worthy of commendation are the choristers of the San Francisco Opera. Most of them took on small solo roles, and all of them sang Sondheim’s rhythmically and tonally challenging music with precision and feeling. The orchestra, led by conductor Patrick Summers, also impressed. A 43-person orchestra for a musical is a rare treat these days, and this one certainly did the score justice, with quick tempi during the songs (though the underscored dialogue sometimes dragged) and lots of energy. It was especially fun to hear an organ in the opera house. The ear-splittingly loud factory whistle was less enjoyable to listen to, atmospheric though it was.

San Francisco Opera’s Sweeney Todd provides the opportunity to hear fabulous singers in roles they wouldn’t usually perform. That alone is well worth the price of admission. But much of what makes this show so fun is simply Sondheim’s brilliant writing, from the terrible puns in “A Little Priest” to the surprise twist ending. Those things aren’t unique to this production, but they should contribute to earning it a large and happy audience.